Video duration -2.5 hours, of a wedding with a lot of transitions,effects and motions

video codec -Jpeg motion

Now i want to export this to a bluray, so i have the following questions/issues after burning two such blurays-

01. It takes 3 hours and some to render it in encore on mpeg 2 settings,single pass. The GPU is constant at 0 % and in the memory cache of the graphic card the available memory is 1025, but it does not exceed 324 mb. Is this normal or are their any bios settings or other settings that i need to be aware of?

02. Is h.264 a better output setting than mpeg 2. Is there any discerenable difference when we view it on a blyray player?

03. In project settings, there are two render settings, mercury software only and other mercury GPU engine, which one of the two gives a better speed/output?